[PATCH v2] lib: fix bitmap_parse() on 64-bit big endian archs

[Alexander Gordeev]

Commit 2d6261583be0 ("lib: rework bitmap_parse()") does not
take into account order of halfwords on 64-bit big endian
architectures. As result (at least) Receive Packet Steering,
IRQ affinity masks and runtime kernel test "test_bitmap" get
broken on s390.

Fixes: 2d6261583be0 ("lib: rework bitmap_parse()")
Cc: stable@xxxxxxxxxxxxxxx
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Yury Norov <yury.norov@xxxxxxxxx>
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: Amritha Nambiar <amritha.nambiar@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Cc: "Tobin C . Harding" <tobin@xxxxxxxxxx>
Cc: Vineet Gupta <vineet.gupta1@xxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Willem de Bruijn <willemb@xxxxxxxxxx>
Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
---
 lib/bitmap.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 89260aa342d6..80d26b183248 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -739,6 +739,7 @@ int bitmap_parse(const char *start, unsigned int buflen,
 	const char *end = strnchrnul(start, buflen, '\n') - 1;
 	int chunks = BITS_TO_U32(nmaskbits);
 	u32 *bitmap = (u32 *)maskp;
+	int chunk = 0;
 	int unset_bit;
 
 	while (1) {
@@ -749,9 +750,14 @@ int bitmap_parse(const char *start, unsigned int buflen,
 		if (!chunks--)
 			return -EOVERFLOW;
 
-		end = bitmap_get_x32_reverse(start, end, bitmap++);
+#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
+		end = bitmap_get_x32_reverse(start, end, &bitmap[chunk ^ 1]);
+#else
+		end = bitmap_get_x32_reverse(start, end, &bitmap[chunk]);
+#endif
 		if (IS_ERR(end))
 			return PTR_ERR(end);
+		chunk++;
 	}
 
 	unset_bit = (BITS_TO_U32(nmaskbits) - chunks) * 32;
-- 
2.23.0